1. Field of the Invention
The present invention relates to an integrated device having a configuration, in which a cantilever and a light source (LED, LD or SEL) are integrated on a single substrate, and applicable to a variety of fields, for example, ultra-fine quantity sensors, and a method for fabricating such a device.
2. Description of the Prior Art
FIG. 1 illustrates a conventional atomic force microscope (AFM) using a light source and a cantilever.
AFM's are adapted to analyze the surface of a sample using a force effecting between atoms in order to observe the sample surface in an atomic magnification. Such AFM's have an advantage in that a variety of samples such as conductors, semiconductors, magnetic substance and dielectric substance can be easily observed in the atmosphere, irrespective of the conductivity of the sample because those AFM's utilize a force effecting between an atom in a local portion of the sample and an atom on the tip of a cantilever. Since the cantilever is constituted by a soft spring, it is bent during its sample scanning operation by a force effecting between the atom on the tip of the cantilever and atoms of the sample. The force causing the cantilever to be bent is measured using an appropriate method. The measured value is then converted into an electrical signal which is, in turn, processed in a reverse feedback manner. Using the resultant signal, it is possible to obtain three-dimensional information about the surface of the sample.
In the case of the AFM shown in FIG. 1, a light beam emitted from a light source 11 is reflected from a cantilever 13 and then incident on a position photodetector 12, so that the position photodetector 12 senses the incident light beam. As shown in FIG. 1, a tip 14 is provided on the lower surface of the cantilever 13 at the free end of the cantilever 13. When the tip 14 approximates to the surface of a sample to be observed, the cantilever 13 is bent due to an attractive force effecting between the sample surface and the tip 14. As a result, a displacement occurs in the cantilever 13. This displacement results in a shift of the light beam which is reflected from the cantilever 13 and then incident on the position photodetector 12. The position photodetector 12 senses such a shift of the incident beam corresponding to a displacement of the cantilever 13. In such a manner, the position photodetector 12 detects even a micro displacement of the cantilever 13.
However, in the case of the conventional AFM, it is difficult to focus the light beam and to align the light source 11 and cantilever 13 with each other because the light source 11 and cantilever 13 are spaced apart from each other. There is also a problem in that a certain space is required because the light source 11 and cantilever 13 should be spaced apart from each other.
Meanwhile, assuming that "L1" and "L2" represent the distance from the light source 11 to the cantilever 13 and the distance from the cantilever 13 to the position photodetector 12, respectively, the amplification rate used in the conversion of a micro displacement of the cantilever 13 into a shift of the light beam is proportional to "L2" while being irrespective of "L1".
In other words, an increase in the distance L2 from the cantilever 13 to the position photodetector 12 results in an increase in the amplification rate. In this case, the micro displacement of the cantilever 13 is correspondingly amplified. Accordingly, the shift of the light beam caused by the displacement of the cantilever 13 is also amplified, so that it is accurately detected by the position photodetector 12. However, the distance L1 between the light source 11 to the cantilever 13 has no influence on the amplification rate.
Therefore, where the light source 11 and cantilever 13 are integrated together on a single substrate while reducing the distance L1 therebetween, it is unnecessary to make a separate effort to align the light source 11 and cantilever 13. In this case, the space occupied by the light source 11 and cantilever 13 is also reduced. Since the light source 11 and cantilever 13 are approximate to each other, the limitation in focusing the light beam is reduced.